The present invention relates to composite golf shafts and in particular to a combination of methods for molding the tip of a golf shaft at a precise angle.
Traditionally golf club shafts have been made straight tapering from a butt section to a narrower tip section which is inserted into the hosel of a golf club head. Typically the butt section includes a grip to enable a golfer to swing the golf club. With the advent of sophisticated molding techniques, it is no longer necessary for the golf club shaft to be at a straight angle. For example, it is well known for putters to have the tip portion of the shaft bent at a precise angle in order to position a golfers hands in a desired location. Similarly, in my U.S. Pat. No. 5,931,741, a hosel-less golf club is disclosed using a single bent shaft, the bend being such that the shaft may enter the club face at various locations and vary between a minimum of five degrees to a maximum of 180 degrees depending in part upon the loft angle of the golf club head.
Other patents of interest are U.S. Pat. No. 3,166,320 to Onions and U.S. Pat. No. 5,255,914 to Schroder, both of which show a wood type golf club head with a hosel and having a bent steel shaft tip which is angularly offset from the main elongated shaft portion of the club.
U.S. Pat. No. 5,465,959 to Cheng relates to a golf club shaft made of a composite material such as carbon graphite fiber and having a bent front section connected to a bent shaft section using a uniform diameter link to couple the parts together. The bent section is formed by wrapping a core with carbon fiber fabric and then thermally pressing it to form the desired shape.
U.S. Pat. No. 5,409,220 to Lombardo shows a putter type golf club head having a bent shaft with the tip offset approximately 20 degrees from the main portion of the shaft. The patent discloses the shaft as being a metal tube substantially hollow between its ends.
The present invention relates to a carbon fiber graphite composite shaft having a bent tip and to a method of making the same. Carbon fiber graphite composite golf shafts are known to be manufactured using a variety of fibers including carbon fiber, fiberglass, Kevlar and the like with carbon fiber being the predominate fiber used. The material is commonly called prepreg or prepreg composite. In a preferred embodiment of manufacturing a bent composite shaft for golf clubs, a mold is fabricated having dimensions specified by the size of the shaft. Two mandrels, a tip mandrel and a main body mandrel, are used with a conventional bladder. The tip mandrel is inserted into the tip end of the bladder at the desired angle, and the main body mandrel is inserted into the opposite end of the bladder, allowing approximately a two inch gap separating the two mandrels inside the bladder at the point where the angle is to be molded in the shaft. The prepreg composite material is then wrapped over the entire bladder and mandrel assembly. The material wrapped over the bend angle area preferably is an intermediate modulus high strain prepreg material or other high strain material such as glass fiber for added strength in this section where additional stresses will occur when a golf ball is struck. All of the wrapped assembly is placed in the mold and compression molded to 300 degrees Fahrenheit for 7-10 minutes or up to 2.5 hours at 250 degrees F. The formed shaft is removed from the press and the mandrels removed. The shaft surface is prepared for finishing, light sanding or other abrasive treatments, as required. Additionally paint may be applied.
An alternate method of producing a composite bent shaft uses a single long one piece flexible mandrel which may be made of flexible silicone or rubberized material, flexible round spiral metal or flexible solid metal. Alternately the above two methods may eliminate the use of an intermediate bladder. When the bladder is not used, the prepreg material is wrapped directly over the mandrels. A mandrel puller will be required to assist in removing mandrels if a bladder is not used.
Still another method contemplates using a permanent elbow connection such as a plastic or rubberized piece that would fit between the two separate tip and main body mandrels which fills the gap between the two mandrels. This elbow connection used without a bladder, permanently remains inside the shaft after the mandrels are removed.
Still other alternate methods includes a mechanical connection between the two mandrels including a screw or mortise and tenon connection for holding the mandrels together.
Still another method is to butt the two ends of the two mandrels up against each other at the desired angle.
Still another method uses a scrim wrap to connect a solid or flexible tip mandrel to a main body mandrel.
An object of the present invention is the provision of a composite golf club shaft having a bent or angular tip section and methods of making the same.
Other objects and advantages of the present invention will become apparent from the following detailed description when viewed in conjunction with the accompanying drawings, which set forth certain embodiments of the invention.